The fuel supply system of a gasoline engine is presently one of the major causes of inefficient engine operation and atmospheric pollution.
The most common device for introducing a mixture of fuel and air into an engine is a carburetor which comprises an air induction passageway formed with a flow restriction, or venturi. The pressure drop in the venturi is utilized to suck liquid gasoline from a reservoir into the induction passageway, where it is atomized and mixed with air to form a combustible mixture. A major drawback of the basic standard carburetor is that the discharge coefficients of air and gasoline in the venturi are unequal, with the result that the ratio of air to fuel decreases as the quantity of air flowing through the venturi increases. A complicated system of second fuel passageways and vents is therefore provided in a standard carburetor to overcome this effect to an extent which allows the engine to be operable. However, even a carburetor provided with such corrective elements often provides an air-fuel ratio which is far from optimum.
An additional problem involved in supplying fuel to an engine is providing a mixture of gasoline and air in which the gasoline is in the form of tiny particles which are thoroughly mixed with the air. The greater the size of the particles, the greater the possiblity of incomplete combustion, resulting in poor fuel economy and the discharge of unburned fuel constituents into the atmosphere. Various attempts have been made to reduce the size of the gasoline particles in the fuel mixture, a common recourse being to heat, or preferably vaporize, the gasoline before mixing it with air. Such a system is disclosed in U.S. Pat. No. 3,738,334 granted June 12, 1973 to R. S. Farr, in which gasoline is heated in a vessel and vaporized gasoline is fed from the upper part of the vessel into a carburetor. Although this system results in increased combustion efficiency, the vaporized gasoline is in the form of droplets of relatively large size compared to the sizes of the molecules of the gasoline constituents.
Other systems are under development in which gasoline is atomized by an ultrasonic generator prior to mixing with air. Although such a system provides gasoline particles of a smaller size than the system of the above discussed patent, the particles are still relatively large compared to the size of the gasoline molecules.